The objective of the proposed research is a comprehensive, systematic and parametric evaluation of and how well the binaural auditory system processes interaural temporal disparities (ITDs) and interaural insensitive disparities (IIDs). The experiments proposed are focused on two general topics: 1) the characterization of the binaural auditory system as a complex cross-correlator, with the interaural correlation derived from the fine-structure for lower frequencies (below 1200 Hz to 1500 Hz or so) and from the envelope for higher frequencies; 2) the ability of the binaural auditory system to utilize dynamically varying interaural information. By producing ITDs and IIDs within and across selected aspects of narrow-band and/or broadband noises, the goal is to extend greatly knowledge of how the human's ability to detect and to discriminate interaural disparities is affected by the spectral region and spectral compositions of sounds that are processed via binaural interactions. One subset of experiments concerns quantifying high-frequency, envelope- based binaural cross-correlation in a manner that is consistent with the listeners' actual processing of the auditory stimulus. The objective is to obtain decisive behavioral data that will determine which index of interaural correlation corresponds best with listeners' performance. A second large subset of experiments will be directed toward measuring sensitivity to dynamically-changing, interaural temporal disparities (ITDs) and interaural insensitive disparities (IIDs) presented within Gaussian, narrow-band noises as a function of their bandwidth and center- frequency. Specialized digital signal-processing techniques developed in our laboratory will permit measurements of sensitivity to dynamically- changing ITDs and IIDs that are independent of the bandwidth of the stimuli. A third subset of experiments will focus on how sensitive listeners' are to abrupt changes in the magnitude of interaural cues. The experiments have been designed to allow an independent, quantitative assessment of the time-constants that describe how well listeners can process changes in binaural information. The last subset of experiments concerns determining how well listeners can discriminate changes in patterns of activity across a putative, two-dimensional, cross- correlation surface whose axes are defined by frequency and interaural delay. The potential health benefits are a better understanding of how the ear and brain process information and the potential for "better" diagnostic procedures that may, eventually, have clinical significance.